1. Field of the Invention
The present invention relates to a wiper control apparatus and method for appropriately controlling the wiping operation of a wiper blade.
2. Description of Related Art
A conventional wiper apparatus for vehicles drives a wiper blade into a reciprocal wiping operation by reversing the direction of rotation of a wiper motor as disclosed in JP 2798733. In this apparatus, pre-reversing positions are set inside of the upper and lower reversing positions of the wiper blade, and a cam switch is provided within the wiper motor to detect the pre-reversing positions and the reversing positions.
Further, in this apparatus, the rotation of the wiper motor is reduced by initiating a PWM control when it is detected that the wiper motor arrives at the pre-reversing position. The rotation of the wiper motor is reversed after the detection of an arrival at the reversing position. As a result, a counter electromotive force which is generated at the reversing position is reduced, so that the wiper blade attains a stable wiping operation.
In the above apparatus, however, the upper and lower reversing positions in the wiping operation are set by the cam switch which is mechanically fixed. The wiping ranges will be set differently in the case that the above control apparatus is applied to wiper devices having different device rigidity from each other or to vehicles having different body rigidity from each other. That is, because the wiping load and the body rigidity differs from vehicle to vehicle, the same predetermined wiping range (wiping angle) cannot be ensured. Thus, an over-running in which the wiper blade is over-driven beyond the predetermined reversing position is likely to occur. In this instance, the cam switch or the like must be changed. Thus, the same motor cannot be applied to the different type of vehicles. Further, it cannot be applied either to the same vehicle type in the case that the vehicle rigidity is different.